A single ended input wideband variable gain low noise amplifier with balanced differential output and digital AGC for CMMB TV tuner

A single-in-differential-out variable gain wideband LNA without on-chip inductor for CMMB TV tuner is implemented in 0.18 µm CMOS. The LNA provide gain modes ranging from 18 dB to −12 dB with a 6dB step. The LNA exhibits an IIP3 of 7.76 dBm and an NF of less than 2.4 dB at 18 dB gain mode. The output imbalance is only 0.01 dB in amplitude and 0.2 degree in phase at 18 dB gain mode. The IIP3 at −12 dB gain mode is 10.2 dBm. The LNA core consumes 6.5 mA from a 1.8 V supply voltage. Gain control is achieved via AGC loop composed of a linear-in-dB power detector and a comparator, which draws a DC current of 1.5 mA. The power sensing time is 500 ns.